Regime demands the removal of monitoring gear. The move would enable it to access, undetected, plutonium to make weapons.

SEOUL — The United States and North Korea marched toward a diplomatic crisis Thursday when the isolated Communist regime said it would reopen shuttered nuclear power facilities and asked the International Atomic Energy Agency to remove monitoring cameras and seals from all of its nuclear facilities.

If implemented, the move would make it more difficult for the international community to know whether North Korea was tapping into its plutonium stockpiles to make nuclear weapons. The CIA has estimated that North Korea already has one or two nuclear devices and could make many more by mid-decade if it used the plutonium at the facilities.

"We view this as a very serious matter," a senior U.S. administration official said late Thursday. "We regret North Korea has decided to make this request. We are consulting with the IAEA and other countries, and we hope North Korea reconsiders their request."

The North Korean announcement came on the heels of the seizure and subsequent release of a ship carrying North Korean-made Scud missiles to Yemen, a move that the regime in Pyongyang, the North's capital, called "unpardonable piracy that wantonly encroached upon" its sovereignty.

The regime said that its hand was forced by a decision last month by the United States and its allies to suspend donations of fuel oil to the power-starved nation. The fuel-oil deliveries, which were cut off after North Korea admitted to a secret uranium-enrichment program, were part of a 1994 agreement that required Pyongyang to give up its nuclear ambitions in exchange for energy assistance.

"With the United States abandoning its responsibility, we now face a discrepancy in our electricity generation plan," said a statement attributed to an unnamed North Korean Foreign Ministry official, who was quoted by the official Korean Central News Agency. As a result, North Korea said it would "immediately resume operation and construction of nuclear facilities."

North Korea did not go so far Thursday as to order the IAEA staff at the sprawling Yongbyon nuclear complex in question to leave.

But the demand to remove the monitoring equipment was seen as especially troubling because it would make it difficult to know whether North Korea was opening any of the 8,000 sealed and canned spent fuel rods at the facility and extracting or reprocessing the plutonium.

Washington's reaction was relatively mild Thursday until it heard about North Korea's demand to remove the cameras from the nuclear facilities.

"The dangerous thing about the request to remove the cameras is, it comes pretty close to a clear admission that they are indeed doing illicit activities," said North Korea expert L. Gordon Flake, executive director of the Mansfield Center for Pacific Affairs in Washington.

"If you're not doing anything wrong ... why do you care about the cameras?"

IAEA head Mohammed Baradei sent a letter back Thursday urging North Korea "to act with restraint in this tense situation and not to take any unilateral action" that would make it difficult for IAEA inspectors to continue monitoring the North Korean facilities.

Baradei also asked North Korea to agree to an urgent meeting of technical experts to discuss monitoring.

North Korea is known for its bold tactics in clamoring for international attention -- and the Bush administration for its refusal to compromise with Pyongyang.

Retired Col. William M. Drennan, a Korea expert at the U.S. Institute of Peace in Washington, said of the North Koreans: "It's not that they're genetically incapable of backing down, though it is rare.... They will back down if they calculate it is their interest to do that."

Cho Myong Chul, a prominent North Korean defector who now works as an economist in Seoul, said that the North Koreans appear to be prodding the Bush administration toward a crisis sooner rather than later with the calculation that they will have more bargaining power when the United States is preoccupied with Iraq."If they wait for the U.S. attack on Iraq to be completed, their room to maneuver will not be as effective," Cho said. "North Korea is clearly very upset, but they are calculating as well. I think they will want to negotiate. They will not start opening the reactor tomorrow."

"Their objective is to get us to negotiate with them," agreed Michael O'Hanlon of the Brookings Institution in Washington, noting that the North Koreans know the United States is preoccupied with Iraq and Afghanistan. "They know right now that we don't want to think about them more than necessary, and not talk to them for a while.... And here is their one way of saying ... 'You have to deal with us now.' "

North Korea's nuclear ambitions precipitated a serious diplomatic crisis with the U.S. in 1994, which ended in that year's deal, known as the Agreed Framework.